1. Field of the Invention
The present invention relates to a differential device, especially a method of manufacturing the same, which comprises a differential mechanism and a differential case housing the differential mechanism, the differential case including: first and second bearing bosses formed integrally therewith on one side portion and other side portion of the differential case and aligned on a same axis; an annular flange formed integrally therewith on an intermediate portion which is offset from a center of the differential case toward the second bearing boss side; work windows for inserting the differential mechanism, the work windows being provided in portions of a peripheral wall of the differential case which face each other on a diametral line orthogonal to the axis; a ring gear press-fitted to an outer peripheral surface of the flange; and a press-fit portion between the flange and the ring gear being welded on the second bearing boss side.
2. Description of the Related Art
Such a differential device is known as disclosed in International Publication No. WO2013-18223.
In a differential device disclosed in International Publication No. WO2013-18223, wall thickness of a flange of a differential case is uniform over an entire periphery, and welding of a press-fit portion between the flange and a ring gear is performed on right and left opposite side portions. Such a structure is effective in reducing welding distortion of the ring gear, but increases the number of welding steps to make manufacturing cost reduction difficult. Moreover, in a case where work windows are formed to be large in order to facilitate inner surface machining of the differential case and insertion of a differential mechanism into the differential case, the work windows may cut into a side surface of the flange on a first bearing boss side to form recessed portions. Such recessed portions interfere with all-around welding of the flange with the ring gear on the opposite side portions, and causes the welding distortion of the ring gear.